Claims:We Claim

1. A method 10 of comparing an actual pressure of fuel that is injected by a fuel injector with a theoretical pressure of fuel that is to be injected by the fuel injector into a single cylinder engine, said method comprising:
determining 12 an actual torque acting on the engine, wherein the actual torque acting on the engine is a function of a crankshaft angular velocity variation in a single combustion cycle, an inertia of the engine, and a speed of the engine;
Determining 14 an actual mass flow rate of fuel that is injected by the fuel injector into the single cylinder engine, wherein the actual mass flow rate of fuel is a function of the actual torque acting on the engine, a thermal efficiency of the engine, a fuel heat value, and a constant value parameter;
determining 16 a theoretical mass flow rate of fuel that is to be injected by the fuel injector into the single cylinder engine, wherein the theoretical mass flow rate of fuel is a function of an orifice diameter of the fuel injector, a rail pressure signal that is obtained from a rail pressure map, an energizing timing of the fuel injector from a energizing timing map, the density of fuel, the dynamic viscosity of fuel, and the length of the orifice of the fuel injector;
determining 18 the actual pressure of fuel that is injected by the fuel injector based on the actual mass flow rate of fuel that is injected by the fuel injector into the single cylinder engine;
determining 20 the theoretical pressure of fuel that is injected by the fuel injector based on the theoretical mass flow rate of fuel that is to be injected by the fuel injector into the single cylinder engine;
comparing 22 the actual pressure of fuel that is injected by the fuel injector with the theoretical pressure of fuel that is injected by the fuel injector into the single cylinder engine based on the determination; and
modifying 24 the actual pressure of fuel that is injected by the fuel injector into the single cylinder engine to equalize it to the theoretical pressure of fuel that is to be injected by the fuel injector into the single cylinder engine based on the comparison of the actual pressure of fuel injected by the fuel injector with the theoretical pressure of fuel that is to be injected by the fuel injector into the single cylinder engine.
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] This invention relates to a single cylinder engine, and more specifically to a method of comparing an actual pressure of fuel that is injected by a fuel injector with a theoretical pressure of fuel that is to be injected by the fuel injector into a single cylinder engine.

Background of the invention
[0002] DE 19931985 A1 describes measuring the angular speed and the angular acceleration and determining the torque sum from the free torque and the mass torque of the oscillating mass. The indicated torque or the indicated pressure of the combustion medium, and hence the energy conversion, are derived from the measured increase in torque on the basis of a polytropic compression of the indicated torque or medium pressure in a crankshaft angle range compression in a cylinder.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a flow chart indicating a method of comparing an actual pressure of fuel that is injected by a fuel injector with a theoretical pressure of fuel that is to be injected by the fuel injector into a single cylinder engine.

Detailed description of the embodiments
[0004] Figure 1 illustrates a flow chart indicating a method 10 of comparing an actual pressure of fuel that is injected by a fuel injector with a theoretical pressure of fuel that is to be injected by the fuel injector into a single cylinder engine. The method comprises determining 12 an actual torque acting on the engine, wherein the actual torque acting on the engine is a function of a crankshaft angular velocity variation in a single combustion cycle, an inertia of the engine, and a speed of the engine, determining 14 an actual mass flow rate of fuel that is injected by the fuel injector into the single cylinder engine, wherein the actual mass flow rate of fuel is a function of the actual torque acting on the engine, a thermal efficiency of the engine, a fuel heat value, and a constant value parameter. The method further comprises determining 16 a theoretical mass flow rate of fuel that is to be injected by the fuel injector into the single cylinder engine, wherein the theoretical mass flow rate of fuel is a function of an orifice diameter of the fuel injector, a rail pressure signal that is obtained from a rail pressure map, an energizing timing of the fuel injector, the density of fuel, the dynamic viscosity of fuel, and the length of the orifice of the fuel injector, and determining 18 the actual pressure of fuel that is injected by the fuel injector based on the actual mass flow rate of fuel that is injected by the fuel injector into the single cylinder engine. In addition, the method comprises determining 20 the theoretical pressure of fuel that is injected by the fuel injector based on the theoretical mass flow rate of fuel that is to be injected by the fuel injector into the single cylinder engine, comparing 22 the actual pressure of fuel that is injected by the fuel injector with the theoretical pressure of fuel that is injected by the fuel injector into the single cylinder engine based on the determination, and modifying 24 the actual pressure of fuel that is injected by the fuel injector into the single cylinder engine to equalize to the theoretical pressure of fuel that is to be injected by the fuel injector into the single cylinder engine based on the comparison of the actual pressure of fuel injected by the fuel injector with the theoretical pressure of fuel that is to be injected by the fuel injector into the single cylinder engine.

[0005] The flow chart indicating a method of comparing an actual pressure of fuel injected by a fuel injector with a theoretical pressure of fuel that is to be injected by the fuel injector into a single cylinder engine comprises determining 12 an actual torque acting on the engine. The actual torque acting on the engine is a function of a crankshaft angular velocity variation in a single combustion cycle, an inertia of the engine, and a speed of the engine. The crankshaft angular velocity variation in the single combustion cycle can be computed graphically by obtaining the difference between the cycle points at the end of the expansion stroke and the end of the compression stroke of the engine. The crankshaft angular velocity is higher at the end of the expansion stroke due to the exhaust gases that push the engine piston towards the bottom dead center than the crankshaft angular velocity at the end of the compression stroke. The inertia of the engine is a constant value, and the engine speed is determined from the engine speed sensor as an engine speed signal. Based on the actual torque that is acting on the engine, an actual mass flow rate of fuel that is injected by the fuel injector into the single cylinder engine is determined. The actual mass flow rate of fuel that is injected by the fuel injector is a function of the actual torque that is acting on the engine, a thermal efficiency of the engine, a fuel heat value, and a constant value parameter, wherein the thermal efficiency of the engine, the fuel heat value, and the constant value parameter are constants.

[0006] The method further comprises determining 16 a theoretical mass flow rate of fuel that is required to be injected by the fuel injector into the single cylinder engine. The theoretical mass flow rate of fuel that is injected by the fuel injector is a function of an orifice diameter of the fuel injector, a rail pressure signal that is obtained from a rail pressure map, an energizing timing of the fuel injector, the density of fuel, the dynamic viscosity of fuel, and the length of the orifice of the fuel injector. The outer diameter of the fuel injector, an energizing timing of the fuel injector, the density of fuel, the dynamic viscosity of fuel, and the length of the orifice of the fuel injector are all constants and have fixed values respectively. Based on the actual mass flow rate of fuel that is injected by the fuel injector into the single cylinder engine, the actual pressure of fuel that is injected by the fuel injector is determined 18. In addition, the method comprises determining 20 the theoretical pressure of fuel that is injected by the fuel injector based on the theoretical mass flow rate of fuel that is injected by the fuel injector into the single cylinder engine.

[0007] The method comprises comparing 22 the actual pressure of fuel that is injected by the fuel injector with the theoretical pressure of fuel that is to be injected by the fuel injector into the single cylinder engine based on the determination of the actual pressure of fuel that is injected by the fuel injector and the theoretical pressure of fuel that is to be injected by the fuel injector. Therein, if the actual pressure of fuel that is injected by the fuel injector into the single cylinder engine is greater or lesser than the theoretical pressure of fuel that is injected by the fuel injector into the single cylinder engine, the actual pressure of fuel that is injected by the fuel injector is modified 24 by decreasing or increasing the actual pressure of fuel that is injected by the fuel injector with respect to the theoretical pressure of fuel that is injected by the fuel injector into the single cylinder engine in order to equalize the actual pressure of fuel that is injected by the fuel injector to the theoretical pressure of fuel that is injected by the fuel injector into the single cylinder engine.

[0008] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard to dimensions of various components are envisaged and form a part of this invention. The scope of the invention is only limited by the scope of the claims.